In a steam supply channel to a steam turbine, a steam governing valve capable of adjusting the supply amount of steam and a steam stop valve capable of stopping the supply of steam are disposed.
For instance, a steam valve device disclosed in Patent Document 1 can be used as the steam governing valve. This steam valve device has a valve body and a flow guide disposed in a recess of the valve body. The valve body, the flow guide, and other component define a steam passage at fully or nearly fully opening degree. This configuration reduces the change in flow passage area of the steam passage at fully or nearly fully opening degree and prevents steam from swirling near the recess, thus suppressing the pressure loss.
On the other hand, a steam valve disclosed in Patent Document 2 includes a stop valve body and a governing valve body, so that a single valve has two functions as the steam stop valve and the steam governing valve. Thus, the use of the steam valve disclosed in Patent Document 2 reduces the pressure loss, compared with the case where the steam stop valve and the steam governing valve are separately prepared.